Re: [syzbot] [bluetooth?] general protection fault in l2cap_sock_recv_cb

Edward Adam Davis
2024-06-15T01:31:32Z

please test null ptr defref in l2cap_sock_recv_cb

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git cc8ed4d0a848

diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index 6db60946c627..d6c2394f0235 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -1241,6 +1241,7 @@ static void l2cap_sock_kill(struct sock *sk)

/* Kill poor orphan */

+ l2cap_pi(sk)->chan->data = NULL;
l2cap_chan_put(l2cap_pi(sk)->chan);
sock_set_flag(sk, SOCK_DEAD);
sock_put(sk);
@@ -1413,6 +1414,7 @@ static int l2cap_sock_release(struct socket *sock)
l2cap_chan_hold(chan);
l2cap_chan_lock(chan);

+ printk("err: %d, sk refcnt: %u, %s\n", err, refcount_read(&sk->sk_refcnt), __func__);
sock_orphan(sk);
l2cap_sock_kill(sk);

@@ -1481,12 +1483,23 @@ static struct l2cap_chan *l2cap_sock_new_connection_cb(struct l2cap_chan *chan)

static int l2cap_sock_recv_cb(struct l2cap_chan *chan, struct sk_buff *skb)
{
- struct sock *sk = chan->data;
- struct l2cap_pinfo *pi = l2cap_pi(sk);
+ struct sock *sk;
+ struct l2cap_pinfo *pi;
int err;

- lock_sock(sk);
+ l2cap_chan_hold(chan);
+ l2cap_chan_lock(chan);
+ sk = chan->data;
+
+ if (!sk) {
+ printk("%s\n", __func__);
+ l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);
+ return -ENXIO;
+ }

+ pi = l2cap_pi(sk);
+ lock_sock(sk);
if (chan->mode == L2CAP_MODE_ERTM && !list_empty(&pi->rx_busy)) {
err = -ENOMEM;
goto done;
@@ -1535,6 +1548,8 @@ static int l2cap_sock_recv_cb(struct l2cap_chan *chan, struct sk_buff *skb)

done:
release_sock(sk);
+ l2cap_chan_unlock(chan);
+ l2cap_chan_put(chan);

return err;
}